Heat too high, for just long enough to make it seem done on the outside.

You know how people recommend cooking a ribeye roast? There's a few ways but one of the easiest is to keep it at a low temp in the oven (or smoker), like 250F or so, until it probes to finish temp minus maybe 5F in the center. Then take it out, crank the oven as hot as it goes, and hit it for maybe ten minutes until the outside looks beautiful.

Now imagine skipping the first step. The inside would still be cold and raw when the outside is done... and still cold and raw when the outer layer is overcooked, too.